Field of the Invention
The present invention relates to a light source apparatus, an illumination device, an exposure apparatus, and a device manufacturing method.
Description of the Related Art
Exposure apparatuses that transfer a pattern formed on an original (reticle or the like) onto a substrate (a wafer or the like where the surface thereof is coated with a resist layer) via a projection optical system are employed in a lithography step included in manufacturing steps of semiconductor devices and the like. The exposure apparatus includes an illumination device that illuminates an original with a light flux emitted from a light source apparatus which condenses and emits light flux emitted from a light source. Japanese Patent No. 4640688 discloses a light source apparatus (illumination device) that employs a high pressure mercury lamp as a light source and an elliptical mirror as a condenser. In the light source apparatus, the light emitting point of the high pressure mercury lamp is positioned in the vicinity of the first focal point of the elliptical mirror so as to condense a light flux emitted from the light emitting point in the vicinity of the second focal point of the elliptical mirror. Japanese Patent No. 3151534 discloses a light source apparatus (light source unit) that employs a two-stage structured condenser configured to include an elliptical mirror and a spherical mirror in this order from the first focal point toward the second focal point of the elliptical mirror so as to reduce the maximum incident angle of the light flux condensed thereby. On the other hand, Japanese Patent No. 4705852 discloses a light source apparatus that employs a two-stage structured condenser configured to include a spherical mirror and an elliptical mirror in this order from the first focal point toward the second focal point of the elliptical mirror so as to reduce the condensed diameter of the light flux condensed thereby. Japanese Patent Laid-Open No. 2001-358071 discloses an exposure apparatus that changes an image of a secondary light source which is circular in shape to an annular shape by inserting a circular cone prism into the pupil position of a fly-eye lens on the side of the light source with a lens placed in-between.
However, in these techniques disclosed in the above Patent Documents, the maximum incident angle and the condensed diameter of the light flux condensed by the condenser and the maximum diameter of the condenser mirror(s) constituting the condenser cannot be reduced simultaneously. Thus, there is room for improvement in the utilization of a light flux emitted from a light source more efficiently.